Anthony I. Chou
Bio: Anthony I. Chou is an academic researcher from University of Texas at Austin. The author has contributed to research in topics: Oxide & Gate oxide. The author has an hindex of 8, co-authored 11 publications receiving 250 citations.
TL;DR: In this paper, a trap-assisted tunneling mechanism was proposed to model the stress-induced leakage current (SILC) in ultrathin oxide metal-oxide-semiconductor devices, which accurately describes the electric field dependence of SILC and also predicts the increase, then decrease in SILC, with decreasing oxide thickness.
Abstract: Stress-induced leakage current (SILC) in ultrathin oxide metal–oxide–semiconductor devices has been quantitatively modeled by the trap-assisted tunneling mechanism. These results are compared with experimental data on samples with oxide thickness ranging from 40 to 80 A. This model accurately describes the electric-field dependence of SILC, and also predicts the increase, then decrease in SILC, with decreasing oxide thickness, which is observed experimentally.
TL;DR: In this paper, the reliability of the oxynitrides is characterized using QBD, stress-induced leakage and surface charge and contact potential difference measurements, and it is found that an improvement in reliability can be obtained by reoxidation in an N2O ambient.
Abstract: The vertical scaling of oxide thickness in the ultra large scale integrated era places stringent requirements on oxide quality. In this letter we report optimization studies in the growth of ultrathin oxynitrides in the sub 3 nm range. The oxynitride growth technique used involved self-limiting growth in nitric oxide (NO) followed by reoxidation in oxygen or nitrous oxide (N2O) ambient. This method allows tight control of oxide thickness and resulted in consistently low leakage currents over a range of thicknesses from 2 to 3 nm. The reliability of the oxynitrides is characterized using QBD, stress-induced leakage and surface charge and contact potential difference measurements. Charge-to-breakdown (QBD) data indicate that the reliability of the oxide degrades with increasing nitridation times in an NO ambient. Increasing reoxidation times in O2 have a similar effect. It is found that an improvement in reliability can be obtained by reoxidation in an N2O ambient. Surprisingly, reoxidizing in N2O proceeds ...
TL;DR: In this article, the effects of fluorine ion implantation into polycrystalline silicon (polysilicon) gate followed by a high-temperature drive-in step have been studied.
Abstract: The effects of fluorine on ultrathin gate oxide and oxynitride (∼40 A) have been studied. The incorporation of fluorine was done by fluorine ion implantation into polycrystalline silicon (polysilicon) gate followed by a high-temperature drive-in step. It has been found that the integrity of oxide has been improved with the incorporation of fluorine as demonstrated by the reduction of stress-induced leakage current and interface trap generation. Furthermore, unlike thicker dielectrics (>100 A) for which the charge-to-breakdown (QBD) values decrease with increasing fluorine concentration, QBD’s remain the same as those of the control samples for the ultrathin thickness regime. The mechanism for oxide quality improvement by F will also be discussed in the letter.
TL;DR: In this paper, the effects of implant doses, sacrificial oxide thicknesses, and gate oxide thickness on gate oxide reliability have been investigated and it was found that there is a tradeoff between oxide thickness control and gate oxidation reliability.
Abstract: Direct nitrogen implant into Si substrate prior to gate oxidation has been proposed to grow multiple gate oxide thicknesses on a single wafer. In this letter, we have studied the reliability of gate oxide grown on nitrogen‐implanted Si substrate. The effects of implant doses, sacrificial oxide thicknesses, and gate oxide thicknesses on gate oxide reliability have been investigated. It was found that there is a tradeoff between oxide thickness control and gate oxide reliability.
TL;DR: The theoretical concepts, experimental tools, and applications of surface photovoltage (SPV) techniques are reviewed in detail in detail as discussed by the authors, where the theoretical discussion is divided into two sections: electrical properties of semiconductor surfaces and the second discusses SPV phenomena.
Abstract: The theoretical concepts, experimental tools, and applications of surface photovoltage (SPV) techniques are reviewed in detail. The theoretical discussion is divided into two sections. The first reviews the electrical properties of semiconductor surfaces and the second discusses SPV phenomena. Next, the most common tools for SPV measurements and their relative advantages and disadvantages are reviewed. These include the Kelvin probe and the use of MIS structures, as well as other less used techniques. Recent novel high-spatial-resolution SPV measurement techniques are also presented. Applications include surface photovoltage spectroscopy (SPS) which is a very effective tool for gap state spectroscopy. An in-depth review of quantitative analyses, which permit the extraction of various important surface and bulk parameters, follows. These analyses include: carrier diffusion length; surface band bending, charge, and dipole; surface and bulk recombination rates; surface state distribution and properties; distinction between surface and bulk states; spectroscopy of thin films, heterostructures and quantum structures; and construction of band diagrams. Finally, concluding remarks are given.
TL;DR: In this paper, the authors summarized recent progress and current scientific understanding of ultrathin (<4 nm) SiO2 and Si-O-N (silicon oxynitride) gate dielectrics on Si-based devices.
Abstract: The outstanding properties of SiO2, which include high resistivity, excellent dielectric strength, a large band gap, a high melting point, and a native, low defect density interface with Si, are in large part responsible for enabling the microelectronics revolution. The Si/SiO2 interface, which forms the heart of the modern metal–oxide–semiconductor field effect transistor, the building block of the integrated circuit, is arguably the worlds most economically and technologically important materials interface. This article summarizes recent progress and current scientific understanding of ultrathin (<4 nm) SiO2 and Si–O–N (silicon oxynitride) gate dielectrics on Si based devices. We will emphasize an understanding of the limits of these gate dielectrics, i.e., how their continuously shrinking thickness, dictated by integrated circuit device scaling, results in physical and electrical property changes that impose limits on their usefulness. We observe, in conclusion, that although Si microelectronic devices...
TL;DR: It is shown that a basic understanding of the gas-phase and thin-film oxygen and nitrogen incorporation chemistries facilitates the processing of layered oxynitride nanostructures with desirable electrical properties.
Abstract: This paper reviews recent progress in understanding microstructural and growth-mechanistic aspects of ultrathin (<4 nm) oxynitride films for gate dielectric applications. Different techniques for characterizing these films are summarized. We discuss several nitridation methods, including thermal (oxy)nitridation in NO, N2O, and N2 as well as a variety of deposition methods. We show that a basic understanding of the gas-phase and thin-film oxygen and nitrogen incorporation chemistries facilitates the processing of layered oxynitride nanostructures with desirable electrical properties.
TL;DR: In this article, a generalized trap-assisted tunneling (GTAT) model is proposed, where an effective tunneling barrier of trapezoidal shape is considered, instead of the triangular barrier utilized in the conventional trap assisted tunneling model.
Abstract: A generalized trap-assisted tunneling (GTAT) model is proposed in this work, where an effective tunneling barrier of trapezoidal shape is considered, instead of the triangular barrier utilized in the conventional trap-assisted tunneling (TAT) model. It is demonstrated that trapezoidal barrier tunneling dominates at low electric fields (E<4 MV/cm), while triangular barrier tunneling contributes the main part of the tunneling current at high electric fields (E=6–8 MV/cm). The comparisons of this improved model and the results of the conventional TAT model at high and low electric fields are discussed. It is concluded that GTAT can more accurately model the current density-electric field (J–E) curves for the conduction enhancement of a trapped oxide film under various deposition conditions over a wider range of electric fields. This is confirmed by the comparative use of both TAT and GTAT models on experimental data obtained from existing reports. Furthermore, a simple method for determining the trap energy ...
TL;DR: In conclusion, silicon oxide is an excellent choice for resistance-switching technologies, offering a number of compelling advantages over competing material systems.
Abstract: Interest in resistance switching is currently growing apace. The promise of novel high-density, low-power, high-speed nonvolatile memory devices is appealing enough, but beyond that there are exciting future possibilities for applications in hardware acceleration for machine learning and artificial intelligence, and for neuromorphic computing. A very wide range of material systems exhibit resistance switching, a number of which-primarily transition metal oxides-are currently being investigated as complementary metal-oxide-semiconductor (CMOS)-compatible technologies. Here, the case is made for silicon oxide, perhaps the most CMOS-compatible dielectric, yet one that has had comparatively little attention as a resistance-switching material. Herein, a taxonomy of switching mechanisms in silicon oxide is presented, and the current state of the art in modeling, understanding fundamental switching mechanisms, and exciting device applications is summarized. In conclusion, silicon oxide is an excellent choice for resistance-switching technologies, offering a number of compelling advantages over competing material systems.